Furnace installation for continuously descaling a metal band

ABSTRACT

A TROUGH IS INCLINED IN A TANK OF MELTED ALKALI-HYDROXIDE AND HAS ITS UPPER INLET END ABOVE THE ALKALI-HYDROXIDE. A METAL BAND IS DESCALED BY BEING PULLED THROUGH MOLTEN SODIUM CONTAINED IN THE TROUGH.

United States Patent Inventors Appl. No.

Filed Patented Assignee Priority FURNACE INSTALLATION FOR CONTINUOUSLYErwin Schumann Rossdorf;

Rudolf Kuhn, Koppel-n, Germany 850,838

Aug. 18, 1969 June 28, 1971 Deutsche Gold-Und Silber-ScheideanstaltVarmals Roesler, Frankfurt (main), (iermany Aug. 27, 1968 GermanyDESCALING A METAL BAND 5 Claims, 1 Drawing Fig.

US. Cl

10 SOLID Nd.

[51] Int. Cl B21c 43/04 [50] Field ot'Search 29/81 (R),

(inquired), 81 (C); 72/39; 266/3, 4 (A)(lnquired) [56] References CitedUNITED STATES PATENTS 1,930,601 10/1933 Townsend 266/4AUX 2,141,38212/1938 Ferm 266/3 2,338,165 1/1944 Caugherty 28/81C 3,182,982 5/1965Ruff 266/3 3,451,840 6/1969 Hough 29/81C Primary Examiner-Alfred R.Guest Attorneys-Francis D. Stephens and Hugo Huettig, Jr.

ABSTRACT: A trough is inclined in a tank of melted alkalihydroxide andhas its upper inlet end above the alkalihydroxide. A metal band isdescaled by being pulled through molten sodium contained in the trough.

lNEET GAS MELTED ALKAL/HYDROX/DE PATENTED JUN28 l9?! /NERT GAS 1O SOL/DNa.-

MELTED ALKAL IHYDROX/DE INVENTORS Erwzln Schumann Rudolf Kuhn FURNACEINSTALLATION FOR CONTINUOUSLY DESCALING A METAL BAND This inventionrelates to a furnace installation for the descaling of endless metalbands in molten sodium with the band running through meltedalkali-hydroxide before and after being passed through the moltensodium.

This installation has the advantage in that only relatively smallamounts of molten sodium are necessary and rolls or cylinders forguiding the metal band through the molten sodium are not necessary.

In this invention, the furnace installation comprises a heated tankcontaining melted alkali-hydroxide in which a sodiumcontaining pipe orchannel is inserted in such a manner that the metal band is immersed inthe molten sodium as it is pulled through the molten sodium by means ofguiding rollers so that the metal band leaving the molten sodium issubmerged in the melted alkali-hydroxide. The line of intersectionbetween the molten sodium and the surface of the melted alkali-hydroxidepasses through the molten sodium.

The means by which the objects of this invention are obtained aredescribed more fully with reference to the accompanying schematicdrawing which is a cross-sectional view through the furnace installationof this invention.

The furnace installation is composed of a heated tank 6 containing themelted alkali-hydroxide, a channel-shaped trough 7, rollers 8a, 8b and8c for guiding the metal band 8d, a protective gas hood 9, a sodiumstorage container connected to a pipe 11, a heating apparatus 12associated with container 10, a segmented wire mesh band or ribbon 13and a driving roller 14 for band 13.

The molten sodium, during the operation of the installation, iscontained in trough 7. The trough is inclined so that its inlet end liesabove the molten alkali-hydroxide while its lower outlet is submerged inthe alkali-hydroxide. The metal band 8d guided by rollers 8b and 8c ispulled through the trough while being immersed in the molten sodium andleaves trough 7 while being submerged in the melted alkali-hydroxide.The molten sodium floats on top of the melted alkali-hydroxide becauseof its lower specific weight. The installation is designed so that theintersecting line between the surface of the alkali-hydroxide and themolten sodium lies within trough 7. In order to protect the sodium frombeing oxidized by the air, a protective inert gas, such as nitrogen orargon, is introduced through pipe 7a into trough 7 at its upper inletend where the metal band 8d enters the trough. In order to reduce theconsumption of the inert gas, the hood 9 has the lower edges of itssides submerged in the melted alkali-hydroxide.

Molten sodium has to be fed or supplied to trough 7 in a continuousmanner in order to maintain the molten sodium at a constant level. Fordoing such, solid sodium is supplied to container 10 and melted in thelower portion of container 10 by means of the heating apparatus 12. Themolten sodium flows by gravity though pipe 11 into trough 7 with pipe 11passing through the melted alkali-hydroxide where the sodium is heatedto the required operation temperaturei The rate of melting the solidsodium is controlled by the height of the sodium within trough 7 so thatwhen the top level of the molten sodium in trough 7 falls below adesired value the heating apparatus 12 is turned on. In order to preventslag or sludge from accumulating in trough 7, a segmented wire mesh band13 is slowly drawn across the bottom of trough 7. Band 13 is driven byroller 14. The slag or sludge thus removed from trough 7 by band 13 isdrawn into the melted alkali-hydroxide from where it can be removed byconventional means.

This invention has the following advantages:

1. The amount of molten sodium in trough 7 can be kept relatively small.if a leak should develop in the trough at some point or another, thenthe further advantage lies in that smaller amounts of molten sodium aremuch easier to handles since then they can be dissolved in the meltedalkali-hydroxide. if large amounts of molten sodium are used, then someof the molten sodium could reach the surface of the melted alkali-hdroxide and violently react with the atmospheric air.

uide rollers lying within the molten sodium are no longer necessary.This eliminates the problem of the material of which the guide rollersare composed with respect to the material reacting with the sodium. inaddition to eliminating the guide rollers in the molten sodium, it isalso possible to eliminate a deflecting roller outside of the bath. Suchshortens the length of the entire installation.

3. Since the molten sodium in this invention has a relatively small freesurface, it is possible to do without the protective gas hood and theinert gas can be introduced into the upper inlet end of the trough 7.However, when a protective hood is used for reducing the consumption ofthe inert or protective gas, then in this invention the hood can be madesubstantially shorter. Furthermore, only one guide roller 8b for themetal band 8d lies within the range of the protective gas which, inturn, means that the number of roller shaft openings through the hood,and thus the number of places to be sealed, are reduced to two.

Having now described the means by which the objects of this inventionare obtained,

We claim:

1. A furnace installation for continuously descaling a metal bandcomprising a heated tank, melted alkali-hydroxide in said tank, aninclined channel-shaped trough in said tank having an upper inlet endabove said alkali-hydroxide and a lower outlet end submerged in saidalkali-hydroxide, a metal band extending through said trough, rollermeans (8b, for pulling said band through said trough, and supply meansfor feeding molten sodium into said trough for immersing said band andwith the point of intersection between the molten sodium and said meltedalkali-hydroxide lying in said trough.

2. An installation as in claim 1, further comprising means forintroducing protective gas into the inlet end of said trough and abovesaid molten sodium.

3. An installation as in claim 1, further comprising a gas hood abovesaid tank and having sides partially submerged in said alkali-hydroxide,and means for introducing protective gas under said hood.

4. An installation as in claim 1, said supply means comprising a sodiumstorage container above said tank, a pipe between said container andsaid trough and extending through said alkali-hydroxide, and heatingmeans for melting the sodium in said tank and feeding the molten sodiumthrough said pipe into said trough at a desired level.

5. An installation as in claim 1, further comprising wire mesh segmentedband means (13) extending along the bottom of said trough, and driveroller means (14) for slowly dragging said segmented band means alongthe bottom of said trough to remove scale and sludge.

